Since the performance of any antenna is altered when placed on an aircraft, the need to accurately characterize the antenna system including the platform effects is critical. The process of experimentally identifying the platform effects of an antenna is difficult and time consuming, since it involves a very large number of measurements of the radiated/scattered fields. This paper identifies a new model based estimation technique that will reduce the number of measurements needed to characterize the antenna system. The model which is determined from a set of field measurements captures the essence of the behavior of the antenna system. Additional field pattern data is then attainable from the model. The new technique is demonstrated on two systems and the results are compared with Prony's estimation technique.